Kyongmo An

Control of propagating spin waves via spin transfer torque in a metallic bilayer waveguide

We investigate the effect of a direct current on propagating spin waves in a CoFeB/Ta bilayer structure. Using the micro-Brillouin light scattering technique, we observe that the spin wave amplitude may be attenuated or amplified depending on the direction of the current and the applied magnetic field. Our work suggests an effective approach for electrically controlling the propagation of spin waves in a magnetic waveguide and may be useful in a number of applications such as phase locked nano-oscillators and hybrid information processing devices.

Interfacial control of Dzyaloshinskii-Moriya interaction in heavy metal/ferromagnetic metal thin film heterostructures

The interfacial Dzyaloshinskii-Moriya interaction (DMI) in ultrathin magnetic thin film heterostructures provides a new approach for controlling spin textures on mesoscopic length scales. Here we investigate the dependence of the interfacial DMI constant

Magnons and Phonons Optically Driven out of Local Equilibrium in a Magnetic Insulator

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Brillouin light scattering spectra as local temperature sensors for thermal magnons and acoustic phonons

on a Pt wedge insertion layer in Ta/CoFeB/Pt(wedge)/MgO thin films by observing the asymmetric spin-wave dispersion using Brillouin light scattering. Continuous tuning of

Deviation from exponential decay for spin waves excited with a coplanar waveguide antenna

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Temperature dependence of Brillouin light scattering spectra of acoustic phonons in silicon

by more than a factor of 3 is realized by inserting less than one monolayer of Pt. The observations provide new insights for designing magnetic thin film heterostructures with tailored

Current control of magnetic anisotropy via stress in a ferromagnetic metal waveguide

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Temperature-dependent Brillouin light scattering spectra of magnons in yttrium iron garnet and permalloy

for controlling skyrmions and magnetic domain-wall chirality and dynamics.

Interfacial Control of Dzyaloshinskii--Moriya Interaction in Heavy Metal/Ferromagnetic Metal Thin Film Heterostructures

The coupling and possible nonequilibrium between magnons and other energy carriers have been used to explain several recently discovered thermally driven spin transport and energy conversion phenomena. Here, we report experiments in which local nonequilibrium between magnons and phonons in a single crystalline bulk magnetic insulator, Y_{3}Fe_{5}O_{12}, has been created optically within a focused laser spot and probed directly via micro-Brillouin light scattering. Through analyzing the deviation in the magnon number density from the local equilibrium value, we obtain the diffusion length of thermal magnons. By explicitly establishing and observing local nonequilibrium between magnons and phonons, our studies represent an important step toward a quantitative understanding of various spin-heat coupling phenomena.

Nanowire spin Hall oscillators: width dependence and spatial mapping

We demonstrate the use of the micro-Brillouin light scattering (micro-BLS) technique as a local temperature sensor for magnons in a permalloy (Py) thin film and phonons in the glass substrate. When the Py film is uniformly heated, we observe a systematic shift in the frequencies of two thermally excited perpendicular standing spin wave modes. Fitting the temperature dependent magnon spectra allows us to achieve a temperature resolution better than 2.5 K. In addition, we demonstrate that the micro-BLS spectra can be used to measure the local temperature of magnons and the relative temperature shift of phonons across a thermal gradient. Such local temperature sensors are useful for investigating spin caloritronic and thermal transport phenomena in general.